It is known in the art to manufacture flexible polyurethane foams using mixtures of methylene bis(phenyl isocyanate) ("MDI") and polymethylene poly(phenyl isocyanate) ("polymeric MDI") and prepolymers based on such mixtures. See, e.g., U.S. Pat. Nos. 4,239,856, 4,256,849, 4,261,852, and 4,365,025. Typical isocyanate reactive materials suggested for use with such isocyanates include (i) mixtures of polyether triols having molecular weights of from 2000 to 7000 with diethanolamine (U.S. Pat. No. 4,239,856); (ii) mixtures of 400 to 10,000 molecular weight polyethers having primary hydroxyl groups with low molecular weight active hydrogen containing materials (U.S. Pat. No. 4,256,849); (iii) polyoxypropylene or poly(oxypropylene-oxyethylene) diols or triols having equivalent weights of from 700 to 2000 (U.S. Pat. No. 4,261,852) and (iv) water (U.S. Pat. No. 4,365,025).
It is also known to use various low molecular weight crosslinkers in the manufacture of flexible foams. U.S. Pat. No. 3,067,148 describes the use of tetrahydric compounds derived from ethylene diamine and alkylene oxides. U.S. Pat. No. 3,948,825 describes the use of reaction products of methylene dianiline and alkylene oxides. U.S. Pat. No. 4,569,952 describes the use of an addition product of an alkylene oxide and an aromatic diamine and a mixture of the addition product with an alkanolamine.
Finally, Dupont has recently introduced an amine sold as Dytek amine for a variety of uses. The Dytek amine is described as 2-methylpentamethylenediamine. Among the uses suggested in product bulletin entitled "Amines" is the use as a chain extender for polyurethanes.
While many foam formulations based on MDI and polymeric MDI give adequate properties for many applications, it is generally difficult to have good processability over a broad isocyanate index range. Additionally, it would be desirable to develop a foam having high tear strength, high elongation, and low compression set for automotive seating and headrests and for nonautomotive seating.